Analysis of transient grounding resistance in time-domain when a number of vertical grounding rods parallel-connected

The transient grounding resistance (TGR) of a number of vertical grounding rods connected by horizontal grounding rods is calculated using FDTD method. The corresponding waveforms of TGR in time-domain under different conditions are illustrated. The following results can be obtained: adding vertical earth electrodes to the horizontal ones can reduce the TGR and the value of TGR decreases with the increasing number of vertical earth electrodes. But when the number of vertical grounding rods increases to a certain number, the TGR doesn´t ´decrease remarkably. In addition, increasing number of vertical earth electrodes is not very effective to decrease TGR when the ground area is limited. And if the quantity of grounding conductor is determined, the deeper and sparsely distributed vertical grounding rods correspond to a lower value of TGR.